System and method for improving asynchronous replication performance in dual controller storage systems

ABSTRACT

A method, computer program product, and computer system for receiving, by a master controller, a request to create a read-only snapshot for an asynchronous source volume, wherein the master controller may be assigned ownership of the read-only snapshot. A peer controller may be assigned as a secondary owner of the read-only snapshot. Ownership of the peer controller as the secondary owner of the read-only snapshot may be revoked based upon a change in metadata of the read-only snapshot. The read-only snapshot may be replicated, asynchronously, from a replication source to a replication destination.

BACKGROUND

In a typical dual controller storage system, ownership of snapshots(e.g., read-only snapshots) may be assigned to only one controller at atime. Storage controllers are generally completely responsible forprocessing of IO requests targeted to snapshots owned by them. Thisdesign may not be efficient for handling IO load targeted to read onlysnapshots.

BRIEF SUMMARY OF DISCLOSURE

In one example implementation, a method, performed by one or morecomputing devices, may include but is not limited to receiving, by amaster controller, a request to create a read-only snapshot for anasynchronous source volume, wherein the master controller may beassigned ownership of the read-only snapshot. A peer controller may beassigned as a secondary owner of the read-only snapshot. Ownership ofthe peer controller as the secondary owner of the read-only snapshot maybe revoked based upon a change in metadata of the read-only snapshot.The read-only snapshot may be replicated, asynchronously, from areplication source to a replication destination.

One or more of the following example features may be included. Themetadata of the read-only snapshot may be synchronized between themaster controller and the peer controller, wherein the peer controllermay be assigned as the secondary owner of the read-only snapshot aftersynchronization the metadata of the read-only snapshot. Replicating,asynchronously, the read-only snapshot to the replication destinationmay include checking validity of the metadata of the read-only snapshoton the peer controller. Replicating, asynchronously, the read-onlysnapshot to the replication destination may include sending a firstcontrol message to the peer controller. Replicating, asynchronously, theread-only snapshot to the replication destination may include sending asecond control message to the replication destination. Replication maybegin after receiving responses associated with the first controlmessage and the second control message. The first control message mayinclude an amount of data to be backed up by the peer controller, andwherein the second control message may include an amount of data to bereplicated to the replication destination from the replication source.

In another example implementation, a computing system may include one ormore processors and one or more memories configured to performoperations that may include but are not limited to receiving, by amaster controller, a request to create a read-only snapshot for anasynchronous source volume, wherein the master controller may beassigned ownership of the read-only snapshot. A peer controller may beassigned as a secondary owner of the read-only snapshot. Ownership ofthe peer controller as the secondary owner of the read-only snapshot maybe revoked based upon a change in metadata of the read-only snapshot.The read-only snapshot may be replicated, asynchronously, from areplication source to a replication destination.

One or more of the following example features may be included. Themetadata of the read-only snapshot may be synchronized between themaster controller and the peer controller, wherein the peer controllermay be assigned as the secondary owner of the read-only snapshot aftersynchronization the metadata of the read-only snapshot. Replicating,asynchronously, the read-only snapshot to the replication destinationmay include checking validity of the metadata of the read-only snapshoton the peer controller. Replicating, asynchronously, the read-onlysnapshot to the replication destination may include sending a firstcontrol message to the peer controller. Replicating, asynchronously, theread-only snapshot to the replication destination may include sending asecond control message to the replication destination. Replication maybegin after receiving responses associated with the first controlmessage and the second control message. The first control message mayinclude an amount of data to be backed up by the peer controller, andwherein the second control message may include an amount of data to bereplicated to the replication destination from the replication source.

In another example implementation, a computer program product may resideon a computer readable storage medium having a plurality of instructionsstored thereon which, when executed across one or more processors, maycause at least a portion of the one or more processors to performoperations that may include but are not limited to receiving, by amaster controller, a request to create a read-only snapshot for anasynchronous source volume, wherein the master controller may beassigned ownership of the read-only snapshot. A peer controller may beassigned as a secondary owner of the read-only snapshot. Ownership ofthe peer controller as the secondary owner of the read-only snapshot maybe revoked based upon a change in metadata of the read-only snapshot.The read-only snapshot may be replicated, asynchronously, from areplication source to a replication destination.

One or more of the following example features may be included. Themetadata of the read-only snapshot may be synchronized between themaster controller and the peer controller, wherein the peer controllermay be assigned as the secondary owner of the read-only snapshot aftersynchronization the metadata of the read-only snapshot. Replicating,asynchronously, the read-only snapshot to the replication destinationmay include checking validity of the metadata of the read-only snapshoton the peer controller. Replicating, asynchronously, the read-onlysnapshot to the replication destination may include sending a firstcontrol message to the peer controller. Replicating, asynchronously, theread-only snapshot to the replication destination may include sending asecond control message to the replication destination. Replication maybegin after receiving responses associated with the first controlmessage and the second control message. The first control message mayinclude an amount of data to be backed up by the peer controller, andwherein the second control message may include an amount of data to bereplicated to the replication destination from the replication source.

The details of one or more example implementations are set forth in theaccompanying drawings and the description below. Other possible examplefeatures and/or possible example advantages will become apparent fromthe description, the drawings, and the claims. Some implementations maynot have those possible example features and/or possible exampleadvantages, and such possible example features and/or possible exampleadvantages may not necessarily be required of some implementations.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is an example diagrammatic view of a replication process coupledto an example distributed computing network according to one or moreexample implementations of the disclosure;

FIG. 2 is an example diagrammatic view of a storage system of FIG. 1according to one or more example implementations of the disclosure;

FIG. 3 is an example diagrammatic view of a storage target of FIG. 1according to one or more example implementations of the disclosure;

FIG. 4 is an example flowchart of a replication process according to oneor more example implementations of the disclosure; and

FIG. 5 is an example diagrammatic view of a storage system environmentwith a replication source and a replication destination according to oneor more example implementations of the disclosure.

Like reference symbols in the various drawings indicate like elements.

DETAILED DESCRIPTION

System Overview:

In some implementations, the present disclosure may be embodied as amethod, system, or computer program product. Accordingly, in someimplementations, the present disclosure may take the form of an entirelyhardware implementation, an entirely software implementation (includingfirmware, resident software, micro-code, etc.) or an implementationcombining software and hardware aspects that may all generally bereferred to herein as a “circuit,” “module” or “system.” Furthermore, insome implementations, the present disclosure may take the form of acomputer program product on a computer-usable storage medium havingcomputer-usable program code embodied in the medium.

In some implementations, any suitable computer usable or computerreadable medium (or media) may be utilized. The computer readable mediummay be a computer readable signal medium or a computer readable storagemedium. The computer-usable, or computer-readable, storage medium(including a storage device associated with a computing device or clientelectronic device) may be, for example, but is not limited to, anelectronic, magnetic, optical, electromagnetic, infrared, orsemiconductor system, apparatus, device, or any suitable combination ofthe foregoing. More specific examples (a non-exhaustive list) of thecomputer-readable medium may include the following: an electricalconnection having one or more wires, a portable computer diskette, ahard disk, a random access memory (RAM), a read-only memory (ROM), anerasable programmable read-only memory (EPROM or Flash memory), anoptical fiber, a portable compact disc read-only memory (CD-ROM), anoptical storage device, a digital versatile disk (DVD), a static randomaccess memory (SRAM), a memory stick, a floppy disk, a mechanicallyencoded device such as punch-cards or raised structures in a groovehaving instructions recorded thereon, a media such as those supportingthe internet or an intranet, or a magnetic storage device. Note that thecomputer-usable or computer-readable medium could even be a suitablemedium upon which the program is stored, scanned, compiled, interpreted,or otherwise processed in a suitable manner, if necessary, and thenstored in a computer memory. In the context of the present disclosure, acomputer-usable or computer-readable, storage medium may be any tangiblemedium that can contain or store a program for use by or in connectionwith the instruction execution system, apparatus, or device.

In some implementations, a computer readable signal medium may include apropagated data signal with computer readable program code embodiedtherein, for example, in baseband or as part of a carrier wave. In someimplementations, such a propagated signal may take any of a variety offorms, including, but not limited to, electro-magnetic, optical, or anysuitable combination thereof. In some implementations, the computerreadable program code may be transmitted using any appropriate medium,including but not limited to the internet, wireline, optical fibercable, RF, etc. In some implementations, a computer readable signalmedium may be any computer readable medium that is not a computerreadable storage medium and that can communicate, propagate, ortransport a program for use by or in connection with an instructionexecution system, apparatus, or device.

In some implementations, computer program code for carrying outoperations of the present disclosure may be assembler instructions,instruction-set-architecture (ISA) instructions, machine instructions,machine dependent instructions, microcode, firmware instructions,state-setting data, or either source code or object code written in anycombination of one or more programming languages, including an objectoriented programming language such as Java®, Smalltalk, C++ or the like.Java® and all Java-based trademarks and logos are trademarks orregistered trademarks of Oracle and/or its affiliates. However, thecomputer program code for carrying out operations of the presentdisclosure may also be written in conventional procedural programminglanguages, such as the “C” programming language, PASCAL, or similarprogramming languages, as well as in scripting languages such asJavascript, PERL, or Python. The program code may execute entirely onthe user's computer, partly on the user's computer, as a stand-alonesoftware package, partly on the user's computer and partly on a remotecomputer or entirely on the remote computer or server. In the latterscenario, the remote computer may be connected to the user's computerthrough a local area network (LAN) or a wide area network (WAN), or theconnection may be made to an external computer (for example, through theinternet using an Internet Service Provider). In some implementations,electronic circuitry including, for example, programmable logiccircuitry, field-programmable gate arrays (FPGAs) or other hardwareaccelerators, micro-controller units (MCUs), or programmable logicarrays (PLAs) may execute the computer readable programinstructions/code by utilizing state information of the computerreadable program instructions to personalize the electronic circuitry,in order to perform aspects of the present disclosure.

In some implementations, the flowchart and block diagrams in the figuresillustrate the architecture, functionality, and operation of possibleimplementations of apparatus (systems), methods and computer programproducts according to various implementations of the present disclosure.Each block in the flowchart and/or block diagrams, and combinations ofblocks in the flowchart and/or block diagrams, may represent a module,segment, or portion of code, which comprises one or more executablecomputer program instructions for implementing the specified logicalfunction(s)/act(s). These computer program instructions may be providedto a processor of a general purpose computer, special purpose computer,or other programmable data processing apparatus to produce a machine,such that the computer program instructions, which may execute via theprocessor of the computer or other programmable data processingapparatus, create the ability to implement one or more of thefunctions/acts specified in the flowchart and/or block diagram block orblocks or combinations thereof. It should be noted that, in someimplementations, the functions noted in the block(s) may occur out ofthe order noted in the figures (or combined or omitted). For example,two blocks shown in succession may, in fact, be executed substantiallyconcurrently, or the blocks may sometimes be executed in the reverseorder, depending upon the functionality involved.

In some implementations, these computer program instructions may also bestored in a computer-readable memory that can direct a computer or otherprogrammable data processing apparatus to function in a particularmanner, such that the instructions stored in the computer-readablememory produce an article of manufacture including instruction meanswhich implement the function/act specified in the flowchart and/or blockdiagram block or blocks or combinations thereof.

In some implementations, the computer program instructions may also beloaded onto a computer or other programmable data processing apparatusto cause a series of operational steps to be performed (not necessarilyin a particular order) on the computer or other programmable apparatusto produce a computer implemented process such that the instructionswhich execute on the computer or other programmable apparatus providesteps for implementing the functions/acts (not necessarily in aparticular order) specified in the flowchart and/or block diagram blockor blocks or combinations thereof.

Referring now to the example implementation of FIG. 1, there is shownreplication process 10 that may reside on and may be executed by acomputer (e.g., computer 12), which may be connected to a network (e.g.,network 14) (e.g., the internet or a local area network). Examples ofcomputer 12 (and/or one or more of the client electronic devices notedbelow) may include, but are not limited to, a storage system (e.g., aNetwork Attached Storage (NAS) system, a Storage Area Network (SAN)), apersonal computer(s), a laptop computer(s), mobile computing device(s),a server computer, a series of server computers, a mainframecomputer(s), or a computing cloud(s). As is known in the art, a SAN mayinclude one or more of the client electronic devices, including a RAIDdevice and a NAS system. In some implementations, each of theaforementioned may be generally described as a computing device. Incertain implementations, a computing device may be a physical or virtualdevice. In many implementations, a computing device may be any devicecapable of performing operations, such as a dedicated processor, aportion of a processor, a virtual processor, a portion of a virtualprocessor, portion of a virtual device, or a virtual device. In someimplementations, a processor may be a physical processor or a virtualprocessor. In some implementations, a virtual processor may correspondto one or more parts of one or more physical processors. In someimplementations, the instructions/logic may be distributed and executedacross one or more processors, virtual or physical, to execute theinstructions/logic. Computer 12 may execute an operating system, forexample, but not limited to, Microsoft® Windows®; Mac® OS X®; Red Hat®Linux®, Windows® Mobile, Chrome OS, Blackberry OS, Fire OS, or a customoperating system. (Microsoft and Windows are registered trademarks ofMicrosoft Corporation in the United States, other countries or both; Macand OS X are registered trademarks of Apple Inc. in the United States,other countries or both; Red Hat is a registered trademark of Red HatCorporation in the United States, other countries or both; and Linux isa registered trademark of Linus Torvalds in the United States, othercountries or both).

In some implementations, as will be discussed below in greater detail, areplication process, such as replication process 10 of FIG. 1, mayreceive, by a master controller, a request to create a read-onlysnapshot for an asynchronous source volume, wherein the mastercontroller may be assigned ownership of the read-only snapshot. A peercontroller may be assigned as a secondary owner of the read-onlysnapshot. Ownership of the peer controller as the secondary owner of theread-only snapshot may be revoked based upon a change in metadata of theread-only snapshot. The read-only snapshot may be replicated,asynchronously, from a replication source to a replication destination.

In some implementations, the instruction sets and subroutines ofreplication process 10, which may be stored on storage device, such asstorage device 16, coupled to computer 12, may be executed by one ormore processors and one or more memory architectures included withincomputer 12. In some implementations, storage device 16 may include butis not limited to: a hard disk drive; all forms of flash memory storagedevices; a tape drive; an optical drive; a RAID array (or other array);a random access memory (RAM); a read-only memory (ROM); or combinationthereof. In some implementations, storage device 16 may be organized asan extent, an extent pool, a RAID extent (e.g., an example 4D+1P R5,where the RAID extent may include, e.g., five storage device extentsthat may be allocated from, e.g., five different storage devices), amapped RAID (e.g., a collection of RAID extents), or combinationthereof.

In some implementations, network 14 may be connected to one or moresecondary networks (e.g., network 18), examples of which may include butare not limited to: a local area network; a wide area network or othertelecommunications network facility; or an intranet, for example. Thephrase “telecommunications network facility,” as used herein, may referto a facility configured to transmit, and/or receive transmissionsto/from one or more mobile client electronic devices (e.g., cellphones,etc.) as well as many others.

In some implementations, computer 12 may include a data store, such as adatabase (e.g., relational database, object-oriented database,triplestore database, etc.) and may be located within any suitablememory location, such as storage device 16 coupled to computer 12. Insome implementations, data, metadata, information, etc. describedthroughout the present disclosure may be stored in the data store. Insome implementations, computer 12 may utilize any known databasemanagement system such as, but not limited to, DB2, in order to providemulti-user access to one or more databases, such as the above notedrelational database. In some implementations, the data store may also bea custom database, such as, for example, a flat file database or an XMLdatabase. In some implementations, any other form(s) of a data storagestructure and/or organization may also be used. In some implementations,replication process 10 may be a component of the data store, astandalone application that interfaces with the above noted data storeand/or an applet/application that is accessed via client applications22, 24, 26, 28. In some implementations, the above noted data store maybe, in whole or in part, distributed in a cloud computing topology. Inthis way, computer 12 and storage device 16 may refer to multipledevices, which may also be distributed throughout the network.

In some implementations, computer 12 may execute a storage managementapplication (e.g., storage management application 21), examples of whichmay include, but are not limited to, e.g., a storage system application,a cloud computing application, a data synchronization application, adata migration application, a garbage collection application, or otherapplication that allows for the implementation and/or management of datain a clustered (or non-clustered) environment (or the like). In someimplementations, replication process 10 and/or storage managementapplication 21 may be accessed via one or more of client applications22, 24, 26, 28. In some implementations, replication process 10 may be astandalone application, or may be an applet/application/script/extensionthat may interact with and/or be executed within storage managementapplication 21, a component of storage management application 21, and/orone or more of client applications 22, 24, 26, 28. In someimplementations, storage management application 21 may be a standaloneapplication, or may be an applet/application/script/extension that mayinteract with and/or be executed within replication process 10, acomponent of replication process 10, and/or one or more of clientapplications 22, 24, 26, 28. In some implementations, one or more ofclient applications 22, 24, 26, 28 may be a standalone application, ormay be an applet/application/script/extension that may interact withand/or be executed within and/or be a component of replication process10 and/or storage management application 21. Examples of clientapplications 22, 24, 26, 28 may include, but are not limited to, e.g., astorage system application, a cloud computing application, a datasynchronization application, a data migration application, a garbagecollection application, or other application that allows for theimplementation and/or management of data in a clustered (ornon-clustered) environment (or the like), a standard and/or mobile webbrowser, an email application (e.g., an email client application), atextual and/or a graphical user interface, a customized web browser, aplugin, an Application Programming Interface (API), or a customapplication. The instruction sets and subroutines of client applications22, 24, 26, 28, which may be stored on storage devices 30, 32, 34, 36,coupled to client electronic devices 38, 40, 42, 44, may be executed byone or more processors and one or more memory architectures incorporatedinto client electronic devices 38, 40, 42, 44.

In some implementations, one or more of storage devices 30, 32, 34, 36,may include but are not limited to: hard disk drives; flash drives, tapedrives; optical drives; RAID arrays; random access memories (RAM); andread-only memories (ROM). Examples of client electronic devices 38, 40,42, 44 (and/or computer 12) may include, but are not limited to, apersonal computer (e.g., client electronic device 38), a laptop computer(e.g., client electronic device 40), a smart/data-enabled, cellularphone (e.g., client electronic device 42), a notebook computer (e.g.,client electronic device 44), a tablet, a server, a television, a smarttelevision, a smart speaker, an Internet of Things (IoT) device, a media(e.g., video, photo, etc.) capturing device, and a dedicated networkdevice. Client electronic devices 38, 40, 42, 44 may each execute anoperating system, examples of which may include but are not limited to,Android™, Apple® iOS®, Mac® OS X®; Red Hat® Linux®, Windows® Mobile,Chrome OS, Blackberry OS, Fire OS, or a custom operating system.

In some implementations, one or more of client applications 22, 24, 26,28 may be configured to effectuate some or all of the functionality ofreplication process 10 (and vice versa). Accordingly, in someimplementations, replication process 10 may be a purely server-sideapplication, a purely client-side application, or a hybridserver-side/client-side application that is cooperatively executed byone or more of client applications 22, 24, 26, 28 and/or replicationprocess 10.

In some implementations, one or more of client applications 22, 24, 26,28 may be configured to effectuate some or all of the functionality ofstorage management application 21 (and vice versa). Accordingly, in someimplementations, storage management application 21 may be a purelyserver-side application, a purely client-side application, or a hybridserver-side/client-side application that is cooperatively executed byone or more of client applications 22, 24, 26, 28 and/or storagemanagement application 21. As one or more of client applications 22, 24,26, 28, replication process 10, and storage management application 21,taken singly or in any combination, may effectuate some or all of thesame functionality, any description of effectuating such functionalityvia one or more of client applications 22, 24, 26, 28, replicationprocess 10, storage management application 21, or combination thereof,and any described interaction(s) between one or more of clientapplications 22, 24, 26, 28, replication process 10, storage managementapplication 21, or combination thereof to effectuate such functionality,should be taken as an example only and not to limit the scope of thedisclosure.

In some implementations, one or more of users 46, 48, 50, 52 may accesscomputer 12 and replication process 10 (e.g., using one or more ofclient electronic devices 38, 40, 42, 44) directly through network 14 orthrough secondary network 18. Further, computer 12 may be connected tonetwork 14 through secondary network 18, as illustrated with phantomlink line 54. Replication process 10 may include one or more userinterfaces, such as browsers and textual or graphical user interfaces,through which users 46, 48, 50, 52 may access replication process 10.

In some implementations, the various client electronic devices may bedirectly or indirectly coupled to network 14 (or network 18). Forexample, client electronic device 38 is shown directly coupled tonetwork 14 via a hardwired network connection. Further, clientelectronic device 44 is shown directly coupled to network 18 via ahardwired network connection. Client electronic device 40 is shownwirelessly coupled to network 14 via wireless communication channel 56established between client electronic device 40 and wireless accesspoint (i.e., WAP) 58, which is shown directly coupled to network 14. WAP58 may be, for example, an IEEE 802.11a, 802.11b, 802.11g, 802.11n,802.11ac, Wi-Fi®, RFID, and/or Bluetooth™ (including Bluetooth™ LowEnergy) device that is capable of establishing wireless communicationchannel 56 between client electronic device 40 and WAP 58. Clientelectronic device 42 is shown wirelessly coupled to network 14 viawireless communication channel 60 established between client electronicdevice 42 and cellular network/bridge 62, which is shown by exampledirectly coupled to network 14.

In some implementations, some or all of the IEEE 802.11x specificationsmay use Ethernet protocol and carrier sense multiple access withcollision avoidance (i.e., CSMA/CA) for path sharing. The various802.11x specifications may use phase-shift keying (i.e., PSK) modulationor complementary code keying (i.e., CCK) modulation, for example.Bluetooth™ (including Bluetooth™ Low Energy) is a telecommunicationsindustry specification that allows, e.g., mobile phones, computers,smart phones, and other electronic devices to be interconnected using ashort-range wireless connection. Other forms of interconnection (e.g.,Near Field Communication (NFC)) may also be used.

In some implementations, various I/O requests (e.g., I/O request 15) maybe sent from, e.g., client applications 22, 24, 26, 28 to, e.g.,computer 12. Examples of I/O request 15 may include but are not limitedto, data write requests (e.g., a request that content be written tocomputer 12) and data read requests (e.g., a request that content beread from computer 12).

Data Storage System:

Referring also to the example implementation of FIGS. 2-3 (e.g., wherecomputer 12 may be configured as a data storage system), computer 12 mayinclude storage processor 100 and a plurality of storage targets (e.g.,storage targets 102, 104, 106, 108, 110). In some implementations,storage targets 102, 104, 106, 108, 110 may include any of theabove-noted storage devices. In some implementations, storage targets102, 104, 106, 108, 110 may be configured to provide various levels ofperformance and/or high availability. For example, storage targets 102,104, 106, 108, 110 may be configured to form a non-fully-duplicativefault-tolerant data storage system (such as a non-fully-duplicative RAIDdata storage system), examples of which may include but are not limitedto: RAID 3 arrays, RAID 4 arrays, RAID 5 arrays, and/or RAID 6 arrays.It will be appreciated that various other types of RAID arrays may beused without departing from the scope of the present disclosure.

While in this particular example, computer 12 is shown to include fivestorage targets (e.g., storage targets 102, 104, 106, 108, 110), this isfor example purposes only and is not intended limit the presentdisclosure. For instance, the actual number of storage targets may beincreased or decreased depending upon, e.g., the level ofredundancy/performance/capacity required.

Further, the storage targets (e.g., storage targets 102, 104, 106, 108,110) included with computer 12 may be configured to form a plurality ofdiscrete storage arrays. For instance, and assuming for example purposesonly that computer 12 includes, e.g., ten discrete storage targets, afirst five targets (of the ten storage targets) may be configured toform a first RAID array and a second five targets (of the ten storagetargets) may be configured to form a second RAID array.

In some implementations, one or more of storage targets 102, 104, 106,108, 110 may be configured to store coded data (e.g., via storagemanagement process 21), wherein such coded data may allow for theregeneration of data lost/corrupted on one or more of storage targets102, 104, 106, 108, 110. Examples of such coded data may include but isnot limited to parity data and Reed-Solomon data. Such coded data may bedistributed across all of storage targets 102, 104, 106, 108, 110 or maybe stored within a specific storage target.

Examples of storage targets 102, 104, 106, 108, 110 may include one ormore data arrays, wherein a combination of storage targets 102, 104,106, 108, 110 (and any processing/control systems associated withstorage management application 21) may form data array 112.

The manner in which computer 12 is implemented may vary depending upone.g., the level of redundancy/performance/capacity required. Forexample, computer 12 may be configured as a SAN (i.e., a Storage AreaNetwork), in which storage processor 100 may be, e.g., a dedicatedcomputing system and each of storage targets 102, 104, 106, 108, 110 maybe a RAID device. An example of storage processor 100 may include but isnot limited to a VPLEX™, VNX™, or Unity™ system offered by Dell EMC™ ofHopkinton, Mass.

In the example where computer 12 is configured as a SAN, the variouscomponents of computer 12 (e.g., storage processor 100, and storagetargets 102, 104, 106, 108, 110) may be coupled using networkinfrastructure 114, examples of which may include but are not limited toan Ethernet (e.g., Layer 2 or Layer 3) network, a fiber channel network,an InfiniB and network, or any other circuit switched/packet switchednetwork.

As discussed above, various I/O requests (e.g., I/O request 15) may begenerated. For example, these I/O requests may be sent from, e.g.,client applications 22, 24, 26, 28 to, e.g., computer 12.Additionally/alternatively (e.g., when storage processor 100 isconfigured as an application server or otherwise), these I/O requestsmay be internally generated within storage processor 100 (e.g., viastorage management process 21). Examples of I/O request 15 may includebut are not limited to data write request 116 (e.g., a request thatcontent 118 be written to computer 12) and data read request 120 (e.g.,a request that content 118 be read from computer 12).

In some implementations, during operation of storage processor 100,content 118 to be written to computer 12 may be received and/orprocessed by storage processor 100 (e.g., via storage management process21). Additionally/alternatively (e.g., when storage processor 100 isconfigured as an application server or otherwise), content 118 to bewritten to computer 12 may be internally generated by storage processor100 (e.g., via storage management process 21).

As discussed above, the instruction sets and subroutines of storagemanagement application 21, which may be stored on storage device 16included within computer 12, may be executed by one or more processorsand one or more memory architectures included with computer 12.Accordingly, in addition to being executed on storage processor 100,some or all of the instruction sets and subroutines of storagemanagement application 21 (and/or replication process 10) may beexecuted by one or more processors and one or more memory architecturesincluded with data array 112.

In some implementations, storage processor 100 may include front endcache memory system 122. Examples of front end cache memory system 122may include but are not limited to a volatile, solid-state, cache memorysystem (e.g., a dynamic RAM cache memory system), a non-volatile,solid-state, cache memory system (e.g., a flash-based, cache memorysystem), and/or any of the above-noted storage devices.

In some implementations, storage processor 100 may initially storecontent 118 within front end cache memory system 122. Depending upon themanner in which front end cache memory system 122 is configured, storageprocessor 100 (e.g., via storage management process 21) may immediatelywrite content 118 to data array 112 (e.g., if front end cache memorysystem 122 is configured as a write-through cache) or may subsequentlywrite content 118 to data array 112 (e.g., if front end cache memorysystem 122 is configured as a write-back cache).

In some implementations, one or more of storage targets 102, 104, 106,108, 110 may include a backend cache memory system. Examples of thebackend cache memory system may include but are not limited to avolatile, solid-state, cache memory system (e.g., a dynamic RAM cachememory system), a non-volatile, solid-state, cache memory system (e.g.,a flash-based, cache memory system), and/or any of the above-notedstorage devices.

Storage Targets:

As discussed above, one or more of storage targets 102, 104, 106, 108,110 may be a RAID device. For instance, and referring also to FIG. 3,there is shown example target 150, wherein target 150 may be one exampleimplementation of a RAID implementation of, e.g., storage target 102,storage target 104, storage target 106, storage target 108, and/orstorage target 110. An example of target 150 may include but is notlimited to a VPLEX™, VNX™, or Unity™ system offered by Dell EMC™ ofHopkinton, Mass. Examples of storage devices 154, 156, 158, 160, 162 mayinclude one or more electro-mechanical hard disk drives, one or moresolid-state/flash devices, and/or any of the above-noted storagedevices. It will be appreciated that while the term “disk” or “drive”may be used throughout, these may refer to and be used interchangeablywith any types of appropriate storage devices as the context andfunctionality of the storage device permits.

In some implementations, target 150 may include storage processor 152and a plurality of storage devices (e.g., storage devices 154, 156, 158,160, 162). Storage devices 154, 156, 158, 160, 162 may be configured toprovide various levels of performance and/or high availability (e.g.,via storage management process 21). For example, one or more of storagedevices 154, 156, 158, 160, 162 (or any of the above-noted storagedevices) may be configured as a RAID 0 array, in which data is stripedacross storage devices. By striping data across a plurality of storagedevices, improved performance may be realized. However, RAID 0 arraysmay not provide a level of high availability. Accordingly, one or moreof storage devices 154, 156, 158, 160, 162 (or any of the above-notedstorage devices) may be configured as a RAID 1 array, in which data ismirrored between storage devices. By mirroring data between storagedevices, a level of high availability may be achieved as multiple copiesof the data may be stored within storage devices 154, 156, 158, 160,162.

While storage devices 154, 156, 158, 160, 162 are discussed above asbeing configured in a RAID 0 or RAID 1 array, this is for examplepurposes only and not intended to limit the present disclosure, as otherconfigurations are possible. For example, storage devices 154, 156, 158,160, 162 may be configured as a RAID 3, RAID 4, RAID 5 or RAID 6 array.

While in this particular example, target 150 is shown to include fivestorage devices (e.g., storage devices 154, 156, 158, 160, 162), this isfor example purposes only and not intended to limit the presentdisclosure. For instance, the actual number of storage devices may beincreased or decreased depending upon, e.g., the level ofredundancy/performance/capacity required.

In some implementations, one or more of storage devices 154, 156, 158,160, 162 may be configured to store (e.g., via storage managementprocess 21) coded data, wherein such coded data may allow for theregeneration of data lost/corrupted on one or more of storage devices154, 156, 158, 160, 162. Examples of such coded data may include but arenot limited to parity data and Reed-Solomon data. Such coded data may bedistributed across all of storage devices 154, 156, 158, 160, 162 or maybe stored within a specific storage device.

The manner in which target 150 is implemented may vary depending upone.g., the level of redundancy/performance/capacity required. Forexample, target 150 may be a RAID device in which storage processor 152is a RAID controller card and storage devices 154, 156, 158, 160, 162are individual “hot-swappable” hard disk drives. Another example oftarget 150 may be a RAID system, examples of which may include but arenot limited to an NAS (i.e., Network Attached Storage) device or a SAN(i.e., Storage Area Network).

In some implementations, storage target 150 may execute all or a portionof storage management application 21. The instruction sets andsubroutines of storage management application 21, which may be stored ona storage device (e.g., storage device 164) coupled to storage processor152, may be executed by one or more processors and one or more memoryarchitectures included with storage processor 152. Storage device 164may include but is not limited to any of the above-noted storagedevices.

As discussed above, computer 12 may be configured as a SAN, whereinstorage processor 100 may be a dedicated computing system and each ofstorage targets 102, 104, 106, 108, 110 may be a RAID device.Accordingly, when storage processor 100 processes data requests 116,120, storage processor 100 (e.g., via storage management process 21) mayprovide the appropriate requests/content (e.g., write request 166,content 168 and read request 170) to, e.g., storage target 150 (which isrepresentative of storage targets 102, 104, 106, 108 and/or 110).

In some implementations, during operation of storage processor 152,content 168 to be written to target 150 may be processed by storageprocessor 152 (e.g., via storage management process 21). Storageprocessor 152 may include cache memory system 172. Examples of cachememory system 172 may include but are not limited to a volatile,solid-state, cache memory system (e.g., a dynamic RAM cache memorysystem) and/or a non-volatile, solid-state, cache memory system (e.g., aflash-based, cache memory system). During operation of storage processor152, content 168 to be written to target 150 may be received by storageprocessor 152 (e.g., via storage management process 21) and initiallystored (e.g., via storage management process 21) within front end cachememory system 172.

In a typical dual controller storage system, ownership ofvolumes/snapshots (e.g., read-only snapshots) may be assigned to onlyone controller at a time. Storage controllers are generally completelyresponsible for processing of IO requests targeted to volumes/snapshotsowned by them, even though the IO requests may be received by the peerstorage controller. This design may not be efficient for handling IOload targeted to read only snapshots. Even though both controllers mayhave access to backend storage and may handle IO requests independently,this capability is not leveraged to make the snapshot reads faster. TheIOs sent to these snapshots are generally only processed by thecontroller which owns the snapshot (e.g., master controller) and theother controller may act as a proxy. This may result in wasted resourcesin the peer and non-utilization of parallel processing power of the peercontroller. For example, asynchronous replication may rely on read-onlysnapshots for copying differential data to remote storage systems.Asynchronous replication time may depend on the size of differentialdata to replicate to remote storage system, and customers may usereplication as one of the means for disaster recovery to protectcritical data spanning, e.g., terabytes to petabytes. The data copy froma replication source may happen from only one controller owning theread-only snapshot to a remote site. Typically, only the master/leadcontroller owning the snapshot may send the data to the remote storagesystem. Snapshot reads may be serialized since read-only snapshots maybe bound to single controller.

In some asynchronous replication designs, the source system may containdifferential data that gets replicated to the destination storagesystem. Even though the source storage system may have two controllersacting in ACTIVE-ACTIVE mode, only one controller may own a snapshot,which may be generally referred to as the master/lead controller forthat volume/snapshot. All data may be pushed to the remote storagesystem via master/lead controller. The ability to simultaneously processreplication IO requests by both controllers on the source storage systemand push the differential data to the remote storage system is not knownto be available in the current designs. Therefore, as will be discussedbelow, the present disclosure may maximize resources of both controllerssimultaneously for efficient copying of differential data from a sourcestorage system to a destination storage system, which may reduceasynchronous replication time significantly.

The Replication Process:

As discussed above and referring also at least to the exampleimplementations of FIGS. 4-5, replication process 10 may receive 400, bya master controller, a request to create a read-only snapshot for anasynchronous source volume, wherein the master controller may beassigned ownership of the read-only snapshot. Replication process 10 mayassign 402 a peer controller as a secondary owner of the read-onlysnapshot. Replication process 10 may revoke 404 ownership of the peercontroller as the secondary owner of the read-only snapshot based upon achange in metadata of the read-only snapshot. Replication process 10 mayreplicate 406, asynchronously, the read-only snapshot from a replicationsource to a replication destination.

In some implementations, replication process 10 may receive 400, by amaster controller, a request to create a read-only snapshot for anasynchronous source volume, wherein the master controller may beassigned ownership of the read-only snapshot. For example, and referringat least to the example implementation of FIG. 5, an example storagesystem environment 500 with a replication source and a replicationdestination is shown. In the example, and for the following discussion,for read-only snapshots of the replication source system, one controllermay be a primary owner (e.g., snapshot lead or controller A) and anothercontroller may act as a secondary owner (e.g., peer controller orcontroller B). As will be discussed below, the controller which is thesecondary owner of the read-only snapshots may also process the IOrequests associated with asynchronous replication. This may result inthe peer controller also participating in pushing the data from thereplication source to the replication destination. Both of thecontrollers may be simultaneously processing the IO requests associatedwith the read-only snapshots, resulting in improved asynchronousreplication performance. It will be appreciated that any portion of thereplication source and/or the replication destination may includeportions of replication process 10.

In the example, the replication source includes the master controller(e.g., lead controller or controller A), which owns the snapshot/volumefor which the read-only snapshot is created. When the read-only snapshotcreation request for an asynchronous source volume is received 400,replication process 10 may flush the cache of the associated volume tothe storage devices (e.g., disks) on the backend storage, and may thencreate the read-only snapshot (using any known technique) for the volumeand make any necessary modifications in the volume metadata. In someimplementations, replication process 10 may synchronize/send to the peercontroller (e.g., controller B on the replication source) replicationand/or read-only snapshot metadata required to identify pages/data ofthe read-only snapshot.

In some implementations, replication process 10 may assign 402 a peercontroller as a secondary owner of the read-only snapshot. For example,after synchronization, replication process 10 may assign 402 the peercontroller (controller B) as the secondary owner of this snapshot. As aresult, the peer controller may now also be capable of performing readoperations to the read-only snapshot independently.

In some implementations, replication process 10 may revoke 404 ownershipof the peer controller as the secondary owner of the read-only snapshotbased upon a change in metadata of the read-only snapshot. For example,based upon any detected change in the snapshot metadata (e.g.,indicating new write data), replication process 10 may revoke 404 thesecondary ownership from the peer controller (non-master).

In some implementations, replication process 10 may synchronize 408 themetadata of the read-only snapshot between the master controller and thepeer controller, wherein the peer controller may be assigned as thesecondary owner of the read-only snapshot after synchronization themetadata of the read-only snapshot. For example, replication process 10may periodically synchronize 408 the read-only snapshot metadata betweenthe master controller and the peer controller on the replication source,and may once again assign ownership to the peer controller (non-master).

In some implementations, replication process 10 may replicate 406,asynchronously, the read-only snapshot from a replication source to areplication destination. However, in some implementations, beforestarting the actual asynchronous replication of the read-only snapshotto the replication destination, one or more steps may be performed forthe replication. For instance, in some implementations, replicating,asynchronously, the read-only snapshot to the replication destinationmay include checking 410 validity of the metadata of the read-onlysnapshot on the peer controller. For example, replication process 10 maycheck 410 the validity of the read-only snapshot metadata on the peercontroller. If the metadata is not up to date, replication process 10may again synchronize the metadata between the master controller and thepeer controller.

In some implementations, replicating, asynchronously, the read-onlysnapshot to the replication destination may include sending 412 a firstcontrol message to the peer controller, and in some implementations, thefirst control message may include an amount of data to be backed up bythe peer controller. For example, replication process 10 may send 412 acontrol message to the peer controller. Among many things, the controlmessage may include how much data needs to be backed up by the peercontroller.

In some implementations, replicating, asynchronously, the read-onlysnapshot to the replication destination may include sending 414 a secondcontrol message to the replication destination, and in someimplementations, the second control message may include an amount ofdata to be replicated to the replication destination from thereplication source. For example, replication process 10 may send 414 acontrol message to the replication agent (which may include a portion ofreplication process 10) on a remote site (e.g., the replicationdestination). The control message may include information such as, e.g.,how much data or how many pages is getting replicated from eachcontroller on the replication source (e.g., controller A/mastercontroller and controller B/peer controller).

In some implementations, replication may begin after receiving responsesassociated with the first control message and the second controlmessage. For example, after receiving the responses from the peercontroller and the remote replication agent (on the replicationdestination), replication process 10 may start replicating thedata/pages from the master controller. Once both responses are received,each controller now knows how much data (or number of pages) need to bepushed from them to the replication destination. Once the peercontroller receives the above-noted control message from the mastercontroller (snapshot lead), the peer controller may send theacknowledgement, and may then start pushing the data from the peercontroller to the replication destination.

Based upon the present disclosure, both the controllers maysimultaneously process I/O requests related to asynchronous replication,and both the controller resources may be used to push data to the remotestorage system. Moreover, asynchronous replication time may be improved,which may be useful in various situations (e.g., where differential datais substantial, such as terabytes or more of data). Additionally, thesame or similar technique described throughout may be used for variousother situations, like cross platform replication where the replicationdestination may be vendor specific, as well as backup applicationsituations, by expediting snapshot reads during backup of a snapshot.

The terminology used herein is for the purpose of describing particularimplementations only and is not intended to be limiting of thedisclosure. As used herein, the singular forms “a”, “an” and “the” areintended to include the plural forms as well, unless the context clearlyindicates otherwise. As used herein, the language “at least one of A, B,and C” (and the like) should be interpreted as covering only A, only B,only C, or any combination of the three, unless the context clearlyindicates otherwise. It will be further understood that the terms“comprises” and/or “comprising,” when used in this specification,specify the presence of stated features, integers, steps (notnecessarily in a particular order), operations, elements, and/orcomponents, but do not preclude the presence or addition of one or moreother features, integers, steps (not necessarily in a particular order),operations, elements, components, and/or groups thereof.

The corresponding structures, materials, acts, and equivalents (e.g., ofall means or step plus function elements) that may be in the claimsbelow are intended to include any structure, material, or act forperforming the function in combination with other claimed elements asspecifically claimed. The description of the present disclosure has beenpresented for purposes of illustration and description, but is notintended to be exhaustive or limited to the disclosure in the formdisclosed. Many modifications, variations, substitutions, and anycombinations thereof will be apparent to those of ordinary skill in theart without departing from the scope and spirit of the disclosure. Theimplementation(s) were chosen and described in order to explain theprinciples of the disclosure and the practical application, and toenable others of ordinary skill in the art to understand the disclosurefor various implementation(s) with various modifications and/or anycombinations of implementation(s) as are suited to the particular usecontemplated.

Having thus described the disclosure of the present application indetail and by reference to implementation(s) thereof, it will beapparent that modifications, variations, and any combinations ofimplementation(s) (including any modifications, variations,substitutions, and combinations thereof) are possible without departingfrom the scope of the disclosure defined in the appended claims.

What is claimed is:
 1. A computer-implemented method comprising:receiving, by a master controller, a request to create a read-onlysnapshot for an asynchronous source volume, wherein the mastercontroller is assigned ownership of the read-only snapshot; flushing, ona backend storage, a cache associated with the asynchronous sourcevolume; creating the read-only snapshot for the asynchronous sourcevolume, wherein creating the read-only snapshot includes modifyingvolume metadata of the asynchronous source volume; assigning a peercontroller as a secondary owner of the read-only snapshot; revokingownership of the peer controller as the secondary owner of the read-onlysnapshot based upon a detected change in the volume metadata of theread-only snapshot of the asynchronous source volume, wherein thedetected change in the volume metadata is indicative of new write datain the read-only snapshot; and replicating, asynchronously, theread-only snapshot from a replication source to a replicationdestination.
 2. The computer-implemented method of claim 1 furthercomprising synchronizing the volume metadata of the read-only snapshotbetween the master controller and the peer controller, wherein the peercontroller is assigned as the secondary owner of the read-only snapshotafter synchronization of the volume metadata of the read-only snapshot.3. The computer-implemented method of claim 1 wherein replicating,asynchronously, the read-only snapshot to the replication destinationincludes checking validity of the volume metadata of the read-onlysnapshot on the peer controller.
 4. The computer-implemented method ofclaim 1 wherein replicating, asynchronously, the read-only snapshot tothe replication destination includes sending a first control message tothe peer controller.
 5. The computer-implemented method of claim 4wherein replicating, asynchronously, the read-only snapshot to thereplication destination includes sending a second control message to thereplication destination.
 6. The computer-implemented method of claim 5wherein replication begins after receiving responses associated with thefirst control message and the second control message.
 7. Thecomputer-implemented method of claim 5 wherein the first control messageincludes an amount of data to be backed up by the peer controller, andwherein the second control message includes an amount of data to bereplicated to the replication destination from the replication source.8. A computer program product residing on a non-transitory computerreadable storage medium having a plurality of instructions storedthereon which, when executed across one or more processors, causes atleast a portion of the one or more processors to perform operationscomprising: receiving, by a master controller, a request to create aread-only snapshot for an asynchronous source volume, wherein the mastercontroller is assigned ownership of the read-only snapshot; flushing, ona backend storage, a cache associated with the asynchronous sourcevolume; creating the read-only snapshot for the asynchronous sourcevolume, wherein creating the read-only snapshot includes modifyingvolume metadata of the asynchronous source volume; assigning a peercontroller as a secondary owner of the read-only snapshot; revokingownership of the peer controller as the secondary owner of the read-onlysnapshot based upon a detected change in the volume metadata of theread-only snapshot of the asynchronous source volume, wherein thedetected change in the volume metadata is indicative of new write datain the read-only snapshot; and replicating, asynchronously, theread-only snapshot from a replication source to a replicationdestination.
 9. The computer program product of claim 8 wherein theoperations further comprise synchronizing the volume metadata of theread-only snapshot between the master controller and the peercontroller, wherein the peer controller is assigned as the secondaryowner of the read-only snapshot after synchronization of the volumemetadata of the read-only snapshot.
 10. The computer program product ofclaim 8 wherein replicating, asynchronously, the read-only snapshot tothe replication destination includes checking validity of the volumemetadata of the read-only snapshot on the peer controller.
 11. Thecomputer program product of claim 8 wherein replicating, asynchronously,the read-only snapshot to the replication destination includes sending afirst control message to the peer controller.
 12. The computer programproduct of claim 11 wherein replicating, asynchronously, the read-onlysnapshot to the replication destination includes sending a secondcontrol message to the replication destination.
 13. The computer programproduct of claim 12 wherein replication begins after receiving responsesassociated with the first control message and the second controlmessage.
 14. The computer program product of claim 13 wherein the firstcontrol message includes an amount of data to be backed up by the peercontroller, and wherein the second control message includes an amount ofdata to be replicated to the replication destination from thereplication source.
 15. A computing system including: one or morememories; and one or more processors configured to perform operationscomprising: receiving, by a master controller, a request to create aread-only snapshot for an asynchronous source volume, wherein the mastercontroller is assigned ownership of the read-only snapshot; flushing, ona backend storage, a cache associated with the asynchronous sourcevolume; creating the read-only snapshot for the asynchronous sourcevolume, wherein creating the read-only snapshot includes modifyingvolume metadata of the asynchronous source volume; assigning a peercontroller as a secondary owner of the read-only snapshot; revokingownership of the peer controller as the secondary owner of the read-onlysnapshot based upon a detected change in the volume metadata of theread-only snapshot of the asynchronous source volume, wherein thedetected change in the volume metadata is indicative of new write datain the read-only snapshot; and replicating, asynchronously, theread-only snapshot from a replication source to a replicationdestination.
 16. The computer program product of claim 15 wherein theoperations further comprise synchronizing the volume metadata of theread-only snapshot between the master controller and the peercontroller, wherein the peer controller is assigned as the secondaryowner of the read-only snapshot after synchronization of the volumemetadata of the read-only snapshot.
 17. The computer program product ofclaim 15 wherein replicating, asynchronously, the read-only snapshot tothe replication destination includes checking validity of the volumemetadata of the read-only snapshot on the peer controller.
 18. Thecomputer program product of claim 15 wherein replicating,asynchronously, the read-only snapshot to the replication destinationincludes sending a first control message to the peer controller, andsending a second control message to the replication destination.
 19. Thecomputer program product of claim 18 wherein replication begins afterreceiving responses associated with the first control message and thesecond control message.
 20. The computer program product of claim 19wherein the first control message includes an amount of data to bebacked up by the peer controller, and wherein the second control messageincludes an amount of data to be replicated to the replicationdestination from the replication source.